Roller Burnishing From a Turret

[Tom S]

Hoping I can tap into some old school knowledge here. I recently picked up a Boyer-Schutz burnishing tool, size 00C for a 5/8" turret (http://www.boyar-schultzsmt.com/burn...ller-c-3kn.htm). Originally my thought had been to see if I could adapt it for use on a tailstock, but shortly after purchasing it I found a turret that I should be able to adapt to my lathe, eliminating the need for that modification. Turret should be here early next week, then getting it mounted on the lathe will be another project.

I can't really find much info on setting up a burnishing tool. I've got W&S's Turret Lathe Operator's Manual, which covers box turning tools with rollers but not burnishing. The material I am hoping to burnish is Nickel Silver, and my goal is to bring it to final size, achieve a good surface finish, and slightly work-harden the surface. I'm thinking to turn the stock to about .0005" oversize using a box tool, then run the burnisher over the surface. From what I understand the rollers on a box tool can have a slight burnishing effect, but from what I'm reading in W&S's book there really shouldn't be much pressure on those rollers (enough to stop with finger pressure). Without much pressure I can't see the really good surface finish or the work hardening happening (correct me if I'm wrong). So how do I set up a roller burnisher? I've got 3 independently adjustable rollers, what's the process to keep things aligned? Do I bring all the rollers in to just touch the work, then adjust only one roller until I get the size I need? I can't see trying to adjust all 3 rollers evenly being a practical solution. Is there any concern with that method that it may cause a taper or the burnishing to be out of round? And do I need a small chamfer to lead the burnisher onto the surface?

TIA

Tom

[dalee100]

Hi,

I've briefly seen one used, but never used one myself.

I would add a lead in chamfer, either 30 or 45 deg. to make the start easier.

Next I would bring the wheels to evenly touch the part. Then make a test run to see what I get. I would add pressure to the wheels until I got the finish and size I wanted. I do suspect it might take a bit more oversize to start than .0005" though. I might start with .001" myself. I suspect starting surface finish will greatly influence final finish and size. So I would strive for the best I could do there.

This seems like a good let's try it situation.

[Doc Nickel]

I can't really find much info on setting up a burnishing tool.

-I haven't really found much on those, either, and I've built up a pretty fair collection of turret lathe/tooling books.

I'm thinking to turn the stock to about .0005" oversize using a box tool, then run the burnisher over the surface.

-I'm not sure if you'll be able to get that kind of consistent accuracy out of a box tool, but it is very much worth a try.

From what I understand the rollers on a box tool can have a slight burnishing effect, but from what I'm reading in W&S's book there really shouldn't be much pressure on those rollers (enough to stop with finger pressure). Without much pressure I can't see the really good surface finish or the work hardening happening (correct me if I'm wrong).

-I'm still quite the neophyte myself on these, but I was given to understand that the "minimal pressure" is at rest- meaning that while the tool is cutting, it'll be trying to push the work into the rollers. (Or, more accurately, trying to push the tool slightly to the side, which adds pressure to the rollers.)

So how do I set up a roller burnisher? I've got 3 independently adjustable rollers, what's the process to keep things aligned?

-Mind you I'm guessing here, but what I'd do is make up a spud the precise size you want the finished part. Mild steel, stainless steel, etc. Something fairly hard-ish, rather than aluminum or brass. Make the surface as smooth and as accurate as possible- remember, you only need a step about 1/2" wide for the rollers.

Chuck that up in the lathe, and set the rollers into contact with it. Do it with the spindle off, and with a little care, you could be able to feel when the wheel makes contact

Do a couple of test cuts, and you'll likely have to "cut and try", adjusting the wheels a tiny bit at a time to sneak up on the final size. (Remember, turret tools like this are "set and forget"- you're supposed to set it once, and then run thousands of parts, so a little extra hassle on setup is irrelevant.)

Do I bring all the rollers in to just touch the work, then adjust only one roller until I get the size I need?

-I'd wager there'll be some experimenting required. And keep in mind that even the best turrets have some slop to them. If you adjust just one wheel half a thou inward, the three-wheel nature of the tool will still self-align. You have to have it in the close ballpark, of course, but if one wheel is a thou or so "off center" of a presumed ideal spindle centerline, it'll still work just fine.

Is there any concern with that method that it may cause a taper or the burnishing to be out of round?

-Taper is unlikely, and if there is, it's due to a taper of the original workpiece, and a box tool makes that sort of thing very nearly impossible. Out of round is presumably very possible, but assuming the work is kept clean and free of loose chips, it should be self-centering and produce an accurate round.

Again, some of this is little better than educated guess, but I have been doing a lot of reading.

And do I need a small chamfer to lead the burnisher onto the surface?

-Almost certainly. Box tools want a little chamfer to start the wheels off, so I'd assume a burnisher would too. Look at the wheels themselves- if they have a radiused lead-in, you can probably get away with just breaking the edge. If they're fairly square, you're going to want a small chamfer to ease the wheels into the work.

Let us know how it comes out.

Doc.

[Rich Carlstedt]

We used Cogsdill Burnishers and you can learn alot at their website with training Videos ect.

https://cogsdill.com/videos/burnishing-tools/

Rich

[Tom S]

Thanks for the notes Doc. Your one thought there makes me wonder if I should keep my eyes open for a set of gauge pins for setup purposes. Should be able to get pretty close to size using a gauge pin in a collet, hopefully a tweak or two from there and I'm off to the races.

Time to make a list of the rest of the tooling I'm going to need to get up and running.